1. Field of the Invention
This invention relates to soft contact lenses made from new copolymers which result in the soft contact lenses having unexpected high tensile modulus of elasticity and tear strength.
It was discovered that the tear strengths and modulus of elasticity properties of certain polysiloxanes could be altered through copolymerization of the polysiloxanes with polycyclic esters of acrylic acid or methacrylic acid.
These contact lenses comprise soft, flexible, fillerless, hydrolytically stable, biologically inert, transparent contact lenses with the capability of transporting oxygen sufficiently to meet the requirements of the human cornea. These contact lenses comprise a polysiloxane monomer .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups copolymerized with monomers comprising isobornyl acrylate, adamantanyl acrylate, dicyclopentadienyl acrylate, menthyl acrylate and isopinocamphyl acrylate, forming a polymer in a cross-linked network having a tensile modulus of elasticity of at least 200 g/mm.sup.2 and a tear strength of at least 5 g/mm thickness.
2. Prior Art Statement
U.S. Pat. No. 4,153,641 teaches contact lenses made from polymers and copolymers comprising poly(organosiloxane) polymers and copolymers formed by polymerizing a poly(organosiloxane) monomer .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups forming a polymer in a crosslinked network. Additionally, specific comonomers are disclosed which include lower esters of acrylic and methacrylic acid, styryls and N-vinyl pyrrolidone which may be copolymerized with the above described poly(organosiloxane) monomer to form a copolymer. The instant invention utilizes the same poly(organosiloxane) monomers described above. However, it was unexpectedly discovered that when the polysiloxane monomers described above were polymerized with a monomer comprising a polycyclic ester of acrylic acid or methacrylic acid, a copolymer was formed which had an unexpectedly high tensile modulus of elasticity and an unexpectedly high tear strength as compared with homopolymers made from the above described polysiloxane monomers. Therefore, the instant copolymers are very suitable for use in making soft contact lenses.
U.S. Pat. No. 4,138,382 teaches, in pertinent part, a hydrophilic, water swellable crosslinked copolymer gel. This copolymer gel is a hydrogel, such as, N-vinylpyrrolidone crosslinked with a low molecular weight siloxane. The siloxane component is a very small constituent and is present for the purpose of crosslinking. The siloxane is not present in amounts more than about 2 percent by weight. U.S. Pat. No. 4,138,382 does not teach the instant copolymers, much less a contact lens made therefrom.
Dutch Pat. No. 7,704,136 published Oct. 18, 1977, teaches, in pertinent part, a wettable siloxane material for use in making contact lenses. However, '136 teaches that the wettable contact lenses should not absorb water since water absorption, as taught in '136, would cause water to be discharged into the eye when the contact lenses are in use. This is viewed as a disadvantage in '136. The Dutch reference further teaches that a lens should not absorb water since, as taught in '136, such a lens is constantly undergoing changes, such as changing its optical properties. '136 further teaches that the handling of such a lens is difficult because it is swellable and physically weak. However, the instant lenses are made from polysiloxane copolymers which are unexpectedly strong, durable and oxygen permeable. Nowhere does this Dutch reference disclose the instant polysiloxanes or the comonomers reacted with these monomeric siloxanes in order to form the copolymers disclosed herein.
U.S. Pat. No. 3,808,178 discloses, in pertinent part, a polymeric material containing a polymethacrylate backbone with relatively short poly(organosiloxane) ester side chains on the backbone polymer. There is no crosslinking involved in '178 since the monomers disclosed in '178 are monofunctional, i.e., have only one functional group on each monomer. In order to get crosslinking in '178 it is taught at column 5 of '178 that different monomers must be added for crosslinking which have more than one functionality. However, in the instant invention crosslinking is obtained since each siloxane monomer is difunctional, i.e., each siloxane monomer contains two functional groups, most preferably two methacrylate groups which results in crosslinking. Therefore, '178 does not teach the polysiloxane monomers used in the instant invention nor the copolymers made therefrom.
Katz and Zewi, "Correlations Between Molecular Structure and Some Bulk Properties of Highly Crosslinked Polysiloxanes", J. Polymer Sci., Vol. 46, Pages 139-148 (1974) teaches, in pertinent part, that divinyl monomers can be prepared by esterification of the carboxyl terminated compounds with two molecules of a monoester of ethylene glycol and a monoester of acrylic acid. Polymerization can be effected by ultraviolet radiation at room temperature. Also taught is the structure as shown on page 146 of the Katz et al article. If this formula was broken down as it relates to the preferred siloxane comonomer taught in the instant application, the formula would be as follows: ##STR1##
In the above formula the R group has an ester linkage whereas in the instant preferred siloxane comonomer the R is a hydrocarbon group.
Also in the above formula the center repeating unit is a dimethyl siloxane unit whereas the center repeating unit in the instant preferred siloxane comonomers may be a paraffin siloxane repeating unit or a diorganosiloxane repeating unit as illustrated below. The R linkage in the Katz et al paper is not as hydrolytically stable as the hydrocarbon linkage in the instant preferred siloxane comonomer. The ester group in Katz et al can be hydrolyzed. This stability is important if this material is to be used in soft contact lenses or biomedical devices since these types of devices are usually heated in order to disinfect them. As mentioned, if the contact lens loses its shape, then it loses its optics. It should be understood that the instant preferred polysiloxane comonomer does have an ester linkage. However, this linkage is between the A and the R groups. It is actually located in the A group as illustrated below by a formula of one of the most preferred monomeric siloxanes of the instant invention. ##STR2##
This Katz et al reference, in addition to teaching the specific formula on page 146, merely teaches that phase differences are detectable as the siloxane chain length is decreased. As the siloxane chain increases in length, Katz et al teaches that the phase differences are lost and these differences merge into one continuous transition.
In addition to the above, it is important to note that Katz et al does not suggest any usage for this material.
Katz and Zewi "Some Rheological Properties of Highly Crosslinked Polysiloxanes" J. Polymer Sci., Vol. 13, pages 645-658 (1975) teaches, in pertinent part, the same materials as taught in the above cited (1974) article by Katz et al. This article teaches in more detail the steps necessary in order to make the starting materials for the polymer as taught in the '74 article. Katz et al is teaching in this article, in pertinent part, how to synethesize the carboxyl terminated siloxane. This is illustrated on pages 646-647. Katz et al then crosslinks this using a different chemical reaction than in the instant application in order to make the polymer as shown on page 649. This polymer is not related in any way to the instant materials. In addition to the above, it is important to note that this Katz et al reference also makes no mention of any uses of the material.
Katz and Zewi "Microheterogeneity in Crosslinked Polysiloxane" J. Polymer Sci., Polymer Chemistry Edition, Vol. 16, pages 597-614 (March, 1978) teaches, in pertinent part, the same materials as taught in the above cited (1974) and (1975) articles by Katz et al. The only new material mentioned appears on page 598, line 8, i.e., crosslinked polyesters. However, these crosslinked polyesters are not pertinent to the instant application. Katz et al is teaching in this article, in pertinent part, how to prepare certain monomers. Katz et al is merely suggesting the same crosslinked material as he suggested in his earlier (1974) and (1975) articles. Katz et al then discusses the physical properties and the microheterogeneity of these crosslinked polymers. He discusses the difference in the phase separation on the submicroscopic scale. As to the physical properties, which Katz et al mentioneed in his article on page 597, he discusses the physical properties in general of polysiloxanes. Katz et al discusses specific properties of his polymers at page 609 where he presents modulus-temperature data. Then he discusses crosslinking efficiency on page 607. He is measuring properties which will give him an idea of his efficiency of crosslinking. Again, it should be stated that Katz et al in this (1978) article teaches no more material than he taught in his earlier articles except for the disclosure of the crosslinked polyesters on page 598. However, these material are not relevant to the instant application. In addition to the above, it is important to note that this Katz reference also makes no mention of any uses of this material except as possible sealants.
W. A. Piccoli, G. G. Haberland and R. L. Merker J. Am. Chem. Soc. "Highly Strained Cyclic Paraffin-Siloxanes" Vol. 82, p. 1883-1885 (Apr. 20, 1960) teaches, in pertinent part, the preparation of the cyclic paraffin-siloxane monomers which may be used in the instant invention to make the preferred siloxane prepolymers of the instant invention. These preferred siloxane prepolymers i.e. linear monomers, in the instant invention are copolymerized and crosslinked to form the preferred polymers used for making contact lenses. It is disclosed on page 1884, column 2, lines 15-27, of the above article that these cyclic paraffin-siloxane monomers may be polymerized using strong acids or bases to form linear polymers. The preferred siloxane linear polymers, as mentioned, are used in the instant invention as preferred prepolymers and copolymerized and crosslinked to form materials for making contact lenses. Nowhere does the article disclose or suggest the crosslinked polymers of the instant invention. Neither does the article suggest or disclose that the polymers can be used to make contact lenses.
R. L. Merker and M. J. Scott J. of Polymer Sci., "The Copolymerization of Cyclic Siloxanes" Vol. 43, p. 297-310 (1960) teaches, in pertinent part, copolymerization studies using cyclic alkyl siloxanes. These materials are copolymerized with silethylene siloxane and then the rates of polymerization are determined. The silethylene siloxane is used because it does not equilibrate between the ring form and the linear form. Once the ring form is broken the ring stays open, that is, the reaction is kept going in one direction. The crosslinked polymers of the instant invention are not suggested or taught by this article nor is the use of the polymers as contact lenses taught or suggested.
U.S. Pat. Nos. 3,041,362 and 3,041,363 teach, in pertinent part, the same materials as taught in the above mentioned articles coauthored by Merker in the J. Am Chem Soc. and J. of Polymer Sci. However, in addition, it is taught that some polyfunctional siloxanes may be used with certain monomers to give crosslinked polymers and copolymers. However, the crosslinked copolymers of the instant invention are not taught or suggested by these references nor are the polymers which are taught by these references even relevent to the instant polymers. Further more, it is not taught or suggested by these references that these polymers could be used as contact lenses.
E. E. Bostick, Kinetics and Mechanisms of Polymerization Vol. 2 (1969) Frisch and Regan, ed. Chapter 8 "Cyclic Siloxanes and Silazanes" p. 343-457, teaches, in pertinent part, siloxane polymerization using cyclic siloxanes. This article teaches no more than the above mentioned article from J. of Polymer Sci. by R. L. Merker and M. J. Scott.
E. E. Bostick, Chemical Reactions of Polymers, High Polymers series vol. 19 (1964) E. M. Fettes, ed. chapter 7 "Interchange Reactions" section B "Silicones" p. 525 teaches, in pertinent part, siloxane copolymerization using cyclic siloxanes. It teaches that these reactions go in one direction. This article teaches no more than the above mentioned article from J. of Polymer Sci. by R. L. Merker and M. J. Scott.
U.S. Pat. No. 2,770,633 discloses 1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane, one of the preferred siloxane monomers used in the instant invention. This is taught at column 1, line 63 of '633 when R equals vinyl. However, '633 teaches only the siloxane monomer whereas the instant invention teaches not only the siloxane monomers but the copolymer made from copolymerization of the polysiloxane monomer with a polycyclic ester of acrylic acid or methacrylic acid to form a polysiloxane material for use in making soft contact lenses. The resulting contact lenses have unexpectedly high tensile modulus of elasticity and an unexpectedly high tear strength. '633 would not want the monomer disclosed in '633 to polymerize since it would not perform its intended function as a lubricant if polymerized.
U.S. Pat. Nos. 3,996,187, 3,006,189, 3,341,490 and 3,228,741 disclose, in pertinent part, contact lenses fabricated from poly(organosiloxanes) containing fillers. The tear strength and tensile strength of the contact lenses made from the instant polymer are of sufficient strength so that no fillers are required.
U.S. Pat. Nos. 3,996,187 and 3,996,189, as mentioned above, disclose contact lenses made from reinforced polysiloxanes. The lenses contain various polysiloxanes with index of refraction similar to the silica filler so that an optically clear silica filled silicone elastomer can be formed from aryl and alkyl siloxanes. The material contains from 5 to 20 percent silica. The silica is used, as mentioned, for strength. The instant invention contains no fillers for strength since the instant material has sufficient strength without fillers.
U.S. Pat. No. 3,341,490 discloses contact lenses made from blends of siloxane copolymers containing reinforcing silica fillers. As mentioned, the contact lenses of the instant invention contain no fillers.
U.S. Pat. No. 3,228,741 discloses contact lenses made from silicone rubber particularly hydrocarbon substituted polysiloxane rubber. This silicone material contains fillers such as pure silica to control flexibility, pliability and resiliency of the lenses. The instant polymers require no fillers.
U.S. Pat. No. 3,518,324 teaches vulcanizing to make silicone rubber whereas the instant invention is concerned with contact lenses made from polymerizing specific monomers.
U.S. Pat. No. 3,878,263 teaches one configuration which may be ##EQU1##
R may be monovalent hydrocarbons.
R' may be a monovalent hydrocarbon.
c may equal zero but when c equals zero then at least one Z must be OR"".
Z is an important ingredient since this is used to crosslink the chains. Therefore, the siloxane monomers of the instant invention are not taught in '263.
U.S. Pat. No. 2,906,735 teaches a reaction between an alkyl siloxane and acrylic acid or a methacrylic acid resulting in a disiloxane terminated by acrylate groups. '735 does not teach the copolymers of the instant invention.
U.S. Pat. No. 2,922,807 discloses disiloxanes having acryloxy or methacryloxy groups attached to the silicone through a divalent alkylene radical of from 2 to 4 carbon atoms.
U.S. Pat. No. 3,763,081 discloses, in pertinent part, the polymerization of an unsaturated siloxane which is somewhat difficult to polymerize since a double bond in this type of monomer generally is not very active. One must use both high temperatures and a peroxide catalysis or a platinum catalysis in order to complete this type of reaction. See, for example, '081 at column 4 lines 35-46. In the instant preferred reaction the siloxane monomeric materials are referred to specifically as having activated unsaturated groups bonded through a divalent hydrocarbon group to the siloxane whereas '081 has no activated unsaturated groups bonded to the siloxane.
U.S. Pat. No. 2,865,885, in pertinent part, teaches a vinyl group which is not activated as shown in column 1, lines 25-30 of '885. The reason '885's double bond is not "active" in the sense as defined in the instant application is that the double bond is bonded to either sulfur or oxygen. In the instant invention, as to the siloxane monomers, this same position would have a ##STR3## carbonyl group. This would make the double bond active, in the instant siloxane monomers, as defined in the instant application. Therefore, '885 since the reactivity ratios are so different i.e. the double bond is not active in '885 as defined in the instant invention, it would be very difficult to get an acceptable copolymerization reaction using the formulae of '885 as compared to the active double bond in the instant siloxane monomers which are easily copolymerized. In the instant invention the vinyl groups are "activated" to facilitate free radical polymerization. The formula given at column 1, lines 25-30 of '885 does not lend itself to free radical polymerization due to the lack of resonance but rather it lends itself to ionic polymerization due to the polar nature of the substituents. Therefore, it would be extremely difficult, if at all possible, for '885 to form the compounds of the instant invention. Also, the compounds formed in '885 are not hydrolytically stable because of the presence of the silicone-nitrogen bond in the formula. The instant invention cannot use a hydrolytically unstable compound. Furthermore, the products of this hydrolysis in '885 could be injurious to the human eye particularly the amines. Also at column 3 of '885 the linkage is an amine linkage to the double bond and in the instant invention this linkage is always an alkyl. Therefore, '885 doe not teach the instant siloxane monomers much less the instant copolymers.
U.S. Pat. No. 2,793,223 teaches, in pertinent part, at Example 5 at column 3, lines 30-41 that a phenyl group is attached to the siloxane. Therefore, that material would be very hard and opaque. This would be unsuitable for contact lenses which must be transparent. Furthermore, contact lenses made from the polymers made from the monomers disclosed in '223, because of the presence of the phenyl group on the siloxane as shown in Example 5 of '223, would not transport oxygen sufficiently whereas contact lenses made from the instant polymers would transport oxygen sufficiently to meet the requirements of the human cornea.